The present invention relates to air-conditioning systems and heat pump systems (in cooling mode) and in particular to methods for calculating expanded target temperature split values, expanded target superheat values, expanded target enthalpy split values and energy efficiency ratio improvements and using the resulting expanded temperature split tables, target superheat tables, and expanded target enthalpy split tables to determine adjustments to refrigerant levels and the energy efficiency ratio improvements resulting from adjustments to refrigerant levels to achieve efficient operation of air-conditioning systems and heat pump systems (in cooling mode) in temperature ranges which cannot be addressed using know mathematics.
Research studies have shown that approximately 50 to 67 percent of air conditioners suffer from improper refrigerant charge and airflow, reducing efficiency by approximately 10 to 50 percent (“National Energy Savings Potential from Addressing HVAC Installation Problems,” US Environmental Protection Agency, 1998; “Assessment of HVAC Installations in New Air Conditioners in the Southern California Edison Service Territory,” Electric Power Research Institute, 1995; “Enhancing the Performance of HVAC and Distribution Systems in Residential New Construction,” Hammarlund, J., et al. 1992 ACEEE Summer Study on Energy Efficiency in Buildings. “Field Measurements of Air Conditioners with and without TXVs,” Mowris, R., Blankenship, A., Jones, E., 2004 ACEEE Summer Study on Energy Efficiency in Buildings, August 2004). Correcting these inefficiencies offers potential savings in the United States obtained from proper refrigerant charge and airflow of approximately 19.6 Billion kilowatt-hours per year and electricity demand savings are approximately 10.3 Million kilowatts.
These inefficiencies are present because most air conditioning technicians do not have proper training, equipment, or verification methods to ensure efficient refrigerant charge and airflow. Instead, technicians rely on rules of thumb such as “add refrigerant until suction line is 6-pack cold or suction pressure is 70 psig or liquid pressure is less than 250 psig.” Air conditioners either do not receive regular service or they are serviced periodically and overcharged due to organizational practices of adding refrigerant charge until the suction line is “6-pack cold.” This practice causes air conditioners to be overcharged and operate inefficiently.
Known methods involve taking measurements of certain temperatures and pressures of a cooling system and determining if the system needs airflow adjustments or refrigerant added or removed. One significant deficiency of the known methods is determining the target temperature split, defined as the target return air dry-bulb temperature minus the target supply air dry-bulb temperature. A prior art temperature split lookup table (Table 1) is shown in FIG. 1. Such known lookup tables are limited to return air dry-bulb temperatures between 70 and 84 degrees Fahrenheit. Unfortunately, the target temperature split is undefined for return air dry-bulb temperatures between 60 and 69 degrees Fahrenheit, return air dry-bulb temperatures between 77 and 84 degrees Fahrenheit, and return air wet-bulb temperatures between 50 and 58 degrees Fahrenheit. Target temperature split values are not present in the upper right corner of Table 1 because the return wet-bulb temperature cannot exceed the return dry-bulb temperature and the relative humidity cannot be greater than 100 percent (under atmospheric conditions).
A prior art superheat table (Table 2) is shown in FIG. 2. Another significant drawback to known lookup tables is that the target superheat temperature, defined as the refrigerant suction line temperature minus the refrigerant evaporator saturation temperature, is limited to condenser air dry-bulb temperatures of 55 to 65 degrees Fahrenheit at return air wet-bulb temperature of 55 degrees Fahrenheit, and condenser air dry-bulb temperature of 115 degrees Fahrenheit at return air wet-bulb temperature of 69 to 76 degrees Fahrenheit. Thus, the target superheat is undefined for condenser air dry-bulb temperatures between 65 and 115 degrees Fahrenheit and return air wet-bulb temperatures between 55 and 69 degrees Fahrenheit.
In many hot and dry climates throughout the world, air conditioning is required to cool interior spaces to maintain indoor comfort. In such hot and dry climates, when technicians diagnose target temperature split for air conditioners or heat pumps in cooling mode, and the return air dry-bulb temperature or return air wet-bulb temperature are in the undefined region using prior art methods, it is impossible to obtain target temperature split to diagnose proper airflow.
In hot and dry climates when technicians attempt to diagnose target superheat for air conditioners or heat pumps in cooling mode, with Fixed Expansion Valve (FXV) systems, and the condenser air dry-bulb temperature and return air wet-bulb temperature are in the undefined region using the prior art tables, it is impossible to obtain an accurate target superheat to diagnose proper refrigerant charge.
The absence of accurate target temperature split and target superheat values cause technicians to improperly diagnose proper temperature split and superheat, leading to significant performance problems with the following results: insufficient airflow; insufficient cooling capacity; liquid refrigerant entering the compressor; excessive mechanical vibration and noise; premature failure of the compressor; reduced energy efficiency performance; and increased electricity consumption.
Further, misdiagnosing a system having improper airflow may result in overcharged and wasting electricity by raising refrigerant pressure and proportionally raising electric power usage. Overcharged systems may also result in liquid refrigerant returning to the compressor causing premature compressor failure. Undercharged air conditioners with improper airflow waste electricity by reducing capacity causing the systems to run more which reduced the life of the compressor causing overheating of the compressor and premature failure.
U.S. Pat. No. 7,500,368 for “System and method for verifying proper refrigerant and airflow for air conditioners and heat pumps in cooling mode” filed by the present Applicant discloses an improved method for obtaining recommended changes to refrigerant levels in an Air Conditioning system. While the '368 patent provides improved methods using existing tables, it is limited to the range target temperature split and target superheat values included in the known tables. The '368 patent is herein incorporated by reference in its entirety.
Unfortunately, the known methods do not compute values required to develop expanded target temperature split and expanded target superheat tables nor do they include computational methods to develop expanded target supply air wet-bulb, relative humidity, and target enthalpy split tables.
A need thus remains for a method to expand target temperature split and target superheat tables.